1. Field of the Invention
The invention relates to an impact absorber for decelerating a vehicle impacting on an obstacle. Such an impact absorber includes two tubes which can be displaced one inside the other in the manner of a telescope. The inner tube is closed off from the outside by a base and has a highly pressurized gas space and a first fluid space. A second fluid space is arranged in the outer tube and is hydraulically connected to the first fluid space via a restriction formed by a restricting aperture in an intermediate wall fixed in the inner tube.
2. Discussion of the Prior Art
Impact absorbers of this type are disclosed, for example, in German reference DE 34 19 165 C2 and German reference DE 38 22 322 C2. In these constructions two tubes which can be displaced one inside the other are used. The tubes include an inner tube, which is closed off from the outside, and has a gas space which is filled with a highly pressurized gas. A first fluid space is likewise located in the inner tube and is separated from the gas space by a separating piston. A restricting disk, which is fixed in the inner tube, is provided with a restricting aperture and hydraulically connects the first fluid space to a second fluid space. When a vehicle collides with an obstacle at a speed of up to 8 km/h, the impact energy is absorbed by the impact absorber with the inner tube plunging into the outer tube. Here, the damping fluid located in the second fluid space is pushed into the first fluid space by means of the restriction, with the result that the separating piston causes the gas cushion in the gas space to be compressed. The increase in volume in the first fluid space takes place counter to the force of the gas space, thereby forming a gas spring. This gas spring also causes the impact absorber to be returned into the initial position. In the event of a high impact speed, an impact absorber of this type, which is usually fixed on stiff support parts of a vehicle, acts virtually as a rigid structure due to the damping force which acts as a function of the speed. So that the deformation zone of a vehicle is effective in this case, a predetermined breaking point is provided on the impact absorber.